Package org.checkerframework.afu.scenelib.util.coll

Class VivifyingMap<K,V>

java.lang.Object

org.checkerframework.afu.scenelib.util.coll.WrapperMap<K,V>

org.checkerframework.afu.scenelib.util.coll.VivifyingMap<K,V>

All Implemented Interfaces:

Map<K,V>

public abstract class VivifyingMap<K,V>
extends WrapperMap<K,V>

A VivifyingMap is a map with two additional methods:

• getVivify(K) is like get, but it never returns null; instead, it stores an empty value and returns that.
• prune() removes empty values

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Field Summary

Fields inherited from class org.checkerframework.afu.scenelib.util.coll.WrapperMap

back

Constructor Summary

Constructors

Constructor	Description
VivifyingMap(Map<K,V> back)	Constructs a new VivifyingMap backed by the given map.

Method Summary

Modifier and Type	Method	Description
protected abstract V	createValueFor(K k)	Returns a new, "empty" value to which the key k can be mapped; subclasses must implement.
V	getVivify(K k)	Like get(), this returns the value to which the specified key is mapped.
protected abstract boolean	isEmptyValue(V v)	Returns true if the given value is "empty" -- that is, it is the same as what getVivify(K) would create.
void	prune()	Prunes this map by deleting entries with empty values.

Methods inherited from class org.checkerframework.afu.scenelib.util.coll.WrapperMap

clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, values

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Details

VivifyingMap

public VivifyingMap(Map<K,V> back)

Constructs a new VivifyingMap backed by the given map. All reads and writes to this VivifyingMap go through to the backing map. However, since the VivifyingMap generally provides a superset of the functionality of the backing map, it is rarely useful to access the backing map directly; the parameter is given mainly so you can provide a new map of your favorite class (HashMap, LinkedHashMap, etc.).

Method Details

getVivify

public V getVivify(K k)

Like get(), this returns the value to which the specified key is mapped. However, this never returns null. If the key is not currently mapped to a value, this method stores a new empty value, then returns that.

createValueFor

protected abstract V createValueFor(K k)

Returns a new, "empty" value to which the key k can be mapped; subclasses must implement.

prune

public void prune()

Prunes this map by deleting entries with empty values.

isEmptyValue

protected abstract boolean isEmptyValue(V v)

Returns true if the given value is "empty" -- that is, it is the same as what getVivify(K) would create.

This method does not recursively prune its argument, and it does not need to.